One of possible causes might be that there is some other program in conflict with Barca.
Particularly if you have some clipboard extender, notetaking program working with clipboard, etc.
Try closing all other programs running, and testing whether it helped, some chances are that it could give us a pointer where to start digging if the issue will disappear.

Is Barca written in Delphi? I was thinking so because I encountered the same problem years ago in my apps, buch much less often.

I solved it by placing all clipboard operations in try except blocks and preventing the dialogs.

e.g.

try
myClip.SetTextBuf(p);
except
end;

The point is that the error dialog is simply wrong (it has surely some cause, but most probably something negligible like a not closed handle).

Barca pops out these errors, but no functionality is lost, all copy, pastes and cuts are always working.

I'm also sure a conflict with a different app is happening (as you suggested), but the point is that Barca is spamming the error dialogs, not any other app (and with spamming I mean up to 10 dialogs a minute).

function lu_PutTextToClipboard(s:string):boolean;begin Result := False; try while not Result do begin if OpenClipboard(Application.Handle) then begin Result := True; Clipboard.AsText := s; CloseClipboard; end else Sleep(5); end; except end;end;

I'm sure Barca writes directly to the Clipboard without checking with OpenClipboard() first if the Clipboard is free to access (Clipboard is not Thread safe!). This causes a bunch of problems with Clipboard Managers.

Yes, it does still exist. The problem is that the Pocomail/Barca Coder assumed the Clipboard Object is instance handled, but there is only one global Clipboard object for all Windows applications. If you access the Clipboard there may be a failure if another program accesses it at the same time. You have to check for such failure and repeat the clipboard operation. Pocomail/Barca displays an ugly error message instead.